Technical Field
Certain embodiments of the invention relates to a plastic working method which performs plastic working on an opening side end portion of a cylindrical material having a bottom, and a spinning machine used in the same, and particularly, to a plastic working method capable of processing a product in which an inner diameter of the opening side end portion is smaller than an inner diameter of a material body, and a spinning machine used in the same.
Description of the Related Art
In the related art, a spinning machine is suggested, which forms a groove portion on an outer circumferential surface in an opening side end portion of a cylindrical material having a bottom and by which a product (for example, a brake piston for a disk brake) in which an inner diameter of the opening side end portion is smaller than an inner diameter of a material body can be obtained with plastic working.